Insulin dependent diabetes mellitus (IDDM) is a chronic autoimmune disease with a strong genetic component. The main component of genetic predisposition maps to the HLA region. The overall goal of this project is to identify the loci and the specific alleles within the HLA region that contribute to IDDM susceptibility. Although the genetic epidemiology of IDDM is complex, recently, molecular approaches based on polymerase chain reaction (PCR) amplification have shown that specific alleles at the Class II loci (in particular at DQB1 ,DQA1, and DRB1) appear to confer susceptibility and resistance. Sequence comparisons of susceptible, neutral, and protective alleles have implicated specific polymorphic residues of the class II molecules as functionally important; however, it is clear that IDDM risk cannot be predicted based on the presence or absence of individual amino acid residues. The determination of HLA class II haplotype frequencies among patients and controls in different ethnic groups has shown that the pattern of disease associations for IDDM can differ in different populations. Detailed molecular typing of the HLA region will help clarify these differences. We propose to carry out PGR/oligonucleotide probe typing for all polymorphic class II loci, using the non-radioactive methods previously developed, on a large number of IDDM families from different ethnic groups, including Mexican-Americans and African-Americans. The use of families allows the unambiguous determination of haplotypes as well as the application of theoretical approaches to determine modes of inheritance and heterogeneity effects. We will also apply HLA class (A,B, and C) PCR/oligonucleotide typing methods (currently under development) as well as PCR methods for typing other potentially relevant polymorphic genes (eg the transporter loci) within the HLA region. Since previous results have suggested that specific combinations of class II alleles can contribute to disease susceptibility, the data will be analyzed with respect to gene interactions. Sequencing of PCR products will allow us to determine the extent of allelic diversity at the HLA region loci and sequence comparisons to identify potentially important residues will be carried out. The analysis of non-HLA region genes in the same families will be explored by our collaborators, allowing us to examine the interactions of HLA and non-HLA genes in IDDM susceptibility. This project should identify the loci and alleles within the HLA region that contribute to IDDM susceptibility and help define the risk for predisposed individuals.